产甲烷菌可通过种间直接电子传递（DIET）方式从与其共生的微生物中获取电子还原CO2产甲烷，从而极大地提高了产甲烷的效率。但是，其共生体内Fdred携带的电子传递到胞外机制及产甲烷菌直接利用胞外电子还原CO2产甲烷机制尚不清楚。因此，本项目拟以G.metallireducens和M.barkeri的co-culture为模型，通过G.sulfurreducens ehr及G.metallireducens act基因突变株代谢乙酸研究以解析G.metallireducens胞内Fdred携带的电子传递到胞外机制，然后通过M.barkeri ech、fpoF、fpo、frh、vho及cytc基因突变株与G.metallireducens耦合代谢丙醇研究以揭示M.barkeri直接利用胞外电子还原CO2产甲烷机制，进而从以上两方面阐明该co-culture通过DIET方式耦合产甲烷机理。

Methanogens can use the electrons obtained directly from the partner of its co-cultures for the reduction of carbon dioxide to methane via direct interspecies electron transfer (DIET), which greatly improves the efficiency of methane production. However, neither has the mechanism through which the electron carried by reduced ferridoxin (Fdred) within electron donor's microorganisms is transferred to extracellular electron acceptors been revealed, nor has the mechanism through which methanogens directly use the electrons obtained from extracellular electron donors for the reduction of carbon dioxide to methane been analyzed to date. . Therefore, the aim of this project is to reveal the mechanism through which the electron carried by Fdred within Geobacter metallireducens is transferred to extracellular electron donors via analyzing Geobacter sulfurreducens Δehr mutant and Geobacter metallireducens Δact mutant metabolizing acetate, and to demonstrate the mechanism through which methanogens directly use the electrons derived from G. metallireducens to reduce carbon dioxide to methane by analyzing the mix-cultures of G. metallireducens and Methanosarcina barkeri mutants (Δech, ΔfpoF, Δfpo, Δfrh, Δvho and Δcytc mutant) stoichiometrically converting propanol to methane with the co-culture of G. metallireducens and M. barkeri as a model co-culture. After that, the mechanism for co-culture of G. metallireducens and M. barkeri stoichiometrically reducing carbon dioxide to methane via DIET will be elucidated by two aspects mentioned above.